Semiconductor Devices and Methods of Manufacture Thereof

ABSTRACT

Semiconductor devices and methods of manufacture thereof are disclosed. In a preferred embodiment, a semiconductor device includes a workpiece having a buried layer disposed beneath a top portion of the workpiece. An isolation ring structure is disposed within the top portion of the workpiece extending completely through at least a portion of the buried layer, the isolation ring structure comprising a ring having an interior region. A diffusion confining structure is disposed within the interior region of the isolation ring structure. A conductive region is disposed within the top portion of the workpiece within a portion of the interior of the isolation ring structure, the conductive region comprising at least one dopant element implanted and diffused into the top portion of the workpiece. The diffusion confining structure defines at least one edge of the conductive region, and the conductive region is coupled to the buried layer.

TECHNICAL FIELD

The present invention relates generally to the fabrication ofsemiconductor devices, and more particularly to the formation of sinkercontact structures in semiconductor devices.

BACKGROUND

Semiconductor devices are used in a variety of electronic applications,such as personal computers, cell phones, digital cameras, and otherelectronic equipment, as examples. Semiconductor devices are typicallyfabricated by sequentially depositing insulating or dielectric layers,conductive layers, and semiconductive layers of material over asemiconductor substrate or workpiece, and patterning the various layersusing lithography to form circuit components and elements thereon.

The upper material layers of semiconductor devices typically comprisemetallization layers that are used to interconnect various electricaldevices and elements formed on an integrated circuit (IC). Themetallization layers are typically formed in a back end of line (BEOL)of a semiconductor manufacturing process, for example. However, thelower layers of semiconductor devices do not typically contain metal,because some metals may contaminate semiconductive materials in someapplications. The fabrication of lower levels of semiconductor devicesthat do not contain metal are often referred to as a front end of line(FEOL) of a semiconductor manufacturing process, for example. Structuresthat are referred to in the art as “sinker contacts” are often used tomake electrical connection in the FEOL to devices formed on asemiconductor workpiece or substrate comprising a conductive buriedlayer, for example.

Sinker contacts are formed by implanting dopants into a substrate, andannealing or heating the substrate to drive the dopants deeper into thesubstrate. The dopants make the semiconductive material conductive, andthus sinker contacts may be used to make electrical contact toconductive buried layers in the substrate. However, since the lateraldiffusion width is on the order of the vertical diffusion depth,conventional sinker contacts are typically quite large, comprising awidth of tens of μm or greater in some applications, for example,requiring a large amount of real estate on an IC, which is costly andlimits the amount that a semiconductor device may be scaled down insize. For example, to provide electrical contact to a 5 μm deep buriedlayer, a total sinker contact width after out-diffusion is typically onthe order of about 15 μm, which is quite large in comparison to today'sstate of the art minimum semiconductor structures that may have a totalwidth of less than about 100 nm.

Thus, what are needed in the art are improved sinker contacts forsemiconductor devices and methods of manufacture thereof.

SUMMARY OF THE INVENTION

These and other problems are generally solved or circumvented, andtechnical advantages are generally achieved, by preferred embodiments ofthe present invention, which provide novel semiconductor devices andmethods of manufacturing thereof.

In accordance with a preferred embodiment of the present invention, asemiconductor device includes a workpiece having a buried layer disposedbeneath a top portion of the workpiece. An isolation ring structure isdisposed within the top portion of the workpiece extending completelythrough at least a portion of the buried layer, the isolation ringstructure comprising a ring having an interior region. A diffusionconfining structure is disposed within the interior region of theisolation ring structure. A conductive region is disposed within the topportion of the workpiece within a portion of the interior of theisolation ring structure, the conductive region comprising at least onedopant element implanted and diffused into the top portion of theworkpiece. The diffusion confining structure defines at least one edgeof the conductive region, and the conductive region is coupled to theburied layer.

The foregoing has outlined rather broadly the features and technicaladvantages of embodiments of the present invention in order that thedetailed description of the invention that follows may be betterunderstood. Additional features and advantages of embodiments of theinvention will be described hereinafter, which form the subject of theclaims of the invention. It should be appreciated by those skilled inthe art that the conception and specific embodiments disclosed may bereadily utilized as a basis for modifying or designing other structuresor processes for carrying out the same purposes of the presentinvention. It should also be realized by those skilled in the art thatsuch equivalent constructions do not depart from the spirit and scope ofthe invention as set forth in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIGS. 1 and 2 show cross-sectional views of a semiconductor device atvarious stages of manufacturing in accordance with an embodiment of thepresent invention, wherein an isolation ring structure and a diffusionconfining structure comprising an isolation trench are formed in aworkpiece;

FIG. 3 shows the semiconductor device shown in FIG. 2 after theworkpiece is masked and a dopant element is implanted into the topsurface of the workpiece in a sinker contact region;

FIG. 4 a shows a top view of the semiconductor device shown in FIG. 3 inaccordance with an embodiment of the present invention, wherein theisolation trench of the diffusion confining structure is elongated yetspaced apart at the ends from the isolation ring structure;

FIG. 4 b shows a top view of the semiconductor device shown in FIG. 3 inaccordance with another embodiment of the present invention, wherein theisolation trench of the diffusion confining structure is segmented;

FIG. 5 illustrates the semiconductor device of FIG. 4 a or 4 b during ananneal step that causes diffusion of the dopant element into theworkpiece, forming a sinker contact that makes electrical contact to aburied layer of the workpiece;

FIG. 6 shows a top view of the embodiment shown in FIGS. 4 a and 5,illustrating that the sinker contact makes electrical contact to theburied layer proximate the ends of the isolation trenches of thediffusion confining structure;

FIGS. 7 and 8 show a cross-sectional view and a top view, respectively,of another preferred embodiment of the present invention, wherein adiffusion confining structure comprises a second isolation ringstructure formed within an interior of a first isolation ring structure,and wherein a sinker contact is formed in an interior of the secondisolation ring structure; and

FIGS. 9 and 10 show a cross-sectional view and a top view, respectively,of another preferred embodiment of the present invention, wherein adiffusion confining structure comprises an isolation trench that extendspartially through the buried layer and completely from one side toanother side of the isolation ring structure.

Corresponding numerals and symbols in the different figures generallyrefer to corresponding parts unless otherwise indicated. The figures aredrawn to clearly illustrate the relevant aspects of the preferredembodiments and are not necessarily drawn to scale.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of the presently preferred embodiments arediscussed in detail below. It should be appreciated, however, that thepresent invention provides many applicable inventive concepts that canbe embodied in a wide variety of specific contexts. The specificembodiments discussed are merely illustrative of specific ways to makeand use the invention, and do not limit the scope of the invention.

The present invention will be described with respect to preferredembodiments in a specific context, namely, in the formation of sinkercontacts in semiconductor devices. Embodiments of the present inventionmay also be applied, however, to other electrical connection structuresand methods of forming thereof in semiconductor devices.

Embodiments of the present invention provide novel semiconductor devicesthat comprise novel sinker contacts and surrounding isolationstructures. A novel isolation structure referred to herein as adiffusion confining structure is formed proximate a sinker contactregion to confine diffusion of dopant elements of the sinker contact.The diffusion confining structures may be formed entirely through aburied layer, with regions of the workpiece between the diffusionconfining structures and an isolation ring structure left intact toprovide electrical contact to the buried layer. In other embodiments,the diffusion confining structures are formed only partially through theburied layer, to provide electrical contact of the sinker contact to theburied layer, to be described further herein.

In accordance with embodiments of the present invention, a workpiece isprovided that includes a buried layer disposed beneath a top portion ofthe workpiece. An isolation ring structure comprising the shape of aring formed around the region where a sinker contact will be formed isdisposed within the top portion of the workpiece extending completelythrough at least a portion of the buried layer. A diffusion confiningstructure is formed within the interior region of the isolation ringstructure. The diffusion confining structure 114 or 314 may comprise atrench, as shown in FIGS. 1 through 4 a, 5, 6, 9 and 10, a segmentedtrench, as shown in FIG. 4 b, or the diffusion confining structure 214may also comprise a trench ring structure, as shown in FIGS. 7 and 8, tobe described further herein. A sinker contact or a conductive region isformed within the top portion of the workpiece within a portion of theinterior of the isolation ring structure. The sinker contact orconductive region comprises at least one dopant element that isimplanted and diffused into the top portion of the workpiece. The sinkercontact is coupled to and makes electrical contact with the buriedlayer. The diffusion confining structure defines at least one edge ofthe sinker contact or conductive region, advantageously, also to bedescribed further herein.

Preferred embodiments of the present invention will next be describedwith reference to FIGS. 1 through 6. FIGS. 1 and 2 show cross-sectionalviews of a semiconductor device 100 at various stages of manufacturingin accordance with a preferred embodiment. Referring first to FIG. 1, aworkpiece 102 is provided. The workpiece 102 may include a semiconductorsubstrate comprising silicon or other semiconductor materials covered byan insulating layer, for example. The workpiece 102 may also includeother active components or circuits, not shown. The workpiece 102 maycomprise silicon oxide over single-crystal silicon, for example. Theworkpiece 102 may include other conductive layers or other semiconductorelements, e.g., transistors, diodes, etc. Compound semiconductors, GaAs,InP, Si/Ge, or SiC, as examples, may be used in place of silicon. Theworkpiece 102 may comprise a silicon-on-insulator (SOI) substrate orgermanium-on-insulator (GOI) substrate, as examples.

A buried layer 104 is formed in the workpiece 102, as shown in FIG. 1.The buried layer 104 preferably comprises a conductive layer that may beformed by implantation of dopants or in-situ deposition of a dopedsemiconductive material, as examples, although the buried layer 104 maybe formed using other methods. The buried layer 104 may comprise adimension d₁ or thickness of about 5 μm, for example, although theburied layer 104 may also comprise other dimensions. The buried layer104 may be formed that has a pattern, for example, not shown (e.g.,rectangular, angled, meandering, or other shapes).

A top portion of the workpiece 102 resides above the buried layer 104,as shown. The top portion of the workpiece 102 may be formed byepitaxial growth of a semiconductive material on top of an implantedburied layer, as an example. Another alternative of forming the buriedlayer 104 is to directly implant the buried layer 104 deep into thesubstrate or workpiece 102 using high-energy implantation, for example.The top portion of the workpiece 102 may comprise a thickness of about 5μm, and may comprise a thickness of about 1 to 10 μm in someembodiments, for example, although alternatively, the top portion of theworkpiece 102 may comprise other dimensions.

The buried layer 104 may comprise N doped silicon in some embodiments,for example, although in some applications, the buried layer 104 maycomprise P doped silicon, as another example. The buried layer 104 maycomprise a sheet layer that is heavily doped so that it is conductive.The buried layer 104 may be coupled to an active area (not shown in thedrawings) of the workpiece 102. The active area may comprise a portionof a transistor, e.g. a bipolar transistor or drain extended MOS (DEMOS)transistor, a diode, capacitor, logic device, memory device, othercircuit elements, or combinations thereof, as examples. The active areacoupled to the buried layer 104 may be formed in the workpiece 102,e.g., before or after the manufacturing processing steps describedherein. It is an object of the present invention to make electricalcontact to the buried layer 104 by forming a sinker contact, forexample, to be described further herein.

Next, a masking material 106 is formed over the workpiece 102. Themasking material 106 may comprise a layer of photosensitive materialsuch as a photoresist, for example. The masking material 106 may alsocomprise a hard mask and a layer of photoresist disposed over the hardmask, for example, not shown.

The masking material 106 is patterned using lithography, e.g., byexposure to light or radiation to transfer a pattern from a lithographymask (not shown) to the masking material 106, and the photosensitivematerial is developed. Exposed portions of the workpiece 102 are etchedaway using the patterned masking material 106 as mask, as shown inphantom in FIG. 1, patterning the workpiece 102 with a plurality oftrenches. The etch process to form the trenches may comprise a wet ordry etch process, for example, and more preferably may comprise areactive ion etch (RIE) process in some embodiments, for example. Theetch process may be anisotropic, isotropic, or a combination thereof,for example. The plurality of trenches comprise patterns for anisolation ring structure 112 and a diffusion confining structure 114shown in FIG. 2, for example.

The trenches may extend lengthwise, e.g., in and out of the paper asshown in FIG. 2 by about several μm to about 1 mm or greater, forexample, as shown in a top view in FIG. 4 a, wherein the trenches havebeen filled with a fill material 108/110. The trenches may extend insubstantially straight lines as shown in FIG. 4 a, or they may comprisearbitrary shapes or paths, e.g., they may be cornered or meandering. Thetrenches may comprise an L-shape, an S-shape, or other shapes across asurface of the workpiece 102. The trenches for the isolation ringstructure 112 are preferably substantially ring-shaped, but may also besquare, rectangular, oval, round, trapezoidal, hexagonal, or othershapes that encapsulate the diffusion confining structure 114 and sinkercontact region, for example.

Preferably, the patterns for the isolation ring structure 112 and thediffusion confining structure 114 are formed simultaneously using asingle etch process, and using a single masking material 106 andlithography mask, for example, although in other embodiments, thepatterns for the isolation ring structure 112 and the diffusionconfining structure 114 may alternatively be formed using two separatelithography processes, for example, not shown.

FIG. 2 shows a cross-sectional view of the semiconductor device 100shown in FIG. 1 after the isolation ring structure 112 and the diffusionconfining structure 114 have been filled with fill materials 108 and110. The trenches for the isolation ring structure 112 and the diffusionconfining structure 114 are preferably filled simultaneously using thesame deposition and/or fill processes, for example. The isolation ringstructure 112 and the diffusion confining structure 114 are preferablyfilled first with an insulating liner 108 and then the remainder of thetrenches for the isolation ring structure 112 and the diffusionconfining structure 114 are filled with a fill material 110 that maycomprise a semiconductive material such as polysilicon or amorphoussilicon in some embodiments, for example.

The optional liner 108 may comprise a nitride, an oxide, or combinationsor multiple layers thereof, for example. The liner 108 may comprise afirst layer of silicon dioxide and a second layer of silicon nitridedisposed over the first layer of silicon dioxide, in some embodiments,for example. The liner 108 preferably comprises a thickness of about 100nm or greater, and more preferably comprise a thickness of about 1 μm orless, for example, although alternatively, the liner 108 may compriseother dimensions, for example. The liner 108 is preferably substantiallyconformal, having the same thickness over all surfaces of the trenches,as shown.

Using a fill material 110 comprising the same material as the workpiece102 may be advantageous in some applications to improve stressproperties of the semiconductor device 100 structure, for example. Usinga fill material 110 that is the same material as the workpiece 102 orhas similar stress properties of the workpiece 102 is advantageousbecause the stress of the workpiece 102 is matched, for example.Alternatively, other materials may be used to fill the isolation ringstructure 112 and the diffusion confining structure 114, for example.

As another example, the isolation ring structure 112 and the diffusionconfining structure 114 may be filled with a liner 108 comprising anoxide or nitride, as examples, and then an insulating fill material 110may be used to fill the remainder of the trenches. The fill material 110may be formed using a high aspect ratio fill process (such as HARP™ byApplied Materials, Inc.), spin-on glass (SOG), FlowFill™ by Trikon, ortetra ethyl oxysilane (TEOS), as examples, although other insulators mayalso be used. The fill material 110 preferably comprises a dielectricmaterial typically used for shallow trench isolation (STI) insemiconductor devices, for example, such as silicon dioxide. The liner108 is optional; alternatively, only a fill material 110 comprising aninsulator may be used to fill the trenches, for example. However,alternatively, other processes and insulating materials may be used tofill the trench. If an isolating liner 108 is used, the trench fillmaterial 110 may also comprise a conductive material, such aspolysilicon or amorphous silicon, which may advantageously reduce stressinside the deep trench structures 112 and 114, for example.

Dimension d₂ in FIG. 2 illustrates the depth and dimension d₃illustrates the width of the diffusion confining structure 114 withinthe workpiece 102. Dimension d₂ may comprise about 20 μm, for example,although alternatively, dimension d₂ may comprise other dimensions.Dimension d₃ may comprise about 3 μm, for example, althoughalternatively, dimension d₃ may comprise other dimensions. Dimension d₄illustrates the width of the isolation ring structure 112. Dimension d₄may comprise about 3 μm, for example, although alternatively, dimensiond₄ may comprise other dimensions.

Dimension d₅ illustrates the distance between the diffusion confiningstructure 114 and the isolation ring structure 112 at a point closest tothe diffusion confining structure 114. Dimension d₅ may comprise about 2to 5 μm, for example, although alternatively, dimension d₅ may compriseother dimensions. Dimension d₆ illustrates the depth of the diffusionconfining structure 114 beneath the buried layer 104. Dimension d₆ maycomprise about 5 μm or less, for example, although alternatively,dimension d₆ may comprise other dimensions. Dimension d₇ illustrates thetotal depth of the isolation ring structure 112. Dimension d₇ maycomprise about 20 μm, for example, although alternatively, dimension d₇may comprise other dimensions.

Dimension d₄ of the isolation ring structure 112 is also referred toherein as a first width (e.g., in the claims), and dimension d₃ of thediffusion confining structure 114 is also referred to herein as a secondwidth. The second width d₃ is preferably substantially the same as thefirst width d₄ in the embodiments shown in FIGS. 1 through 6, forexample. Thus, during the etch process, trenches are formed that havesubstantially the same depth for the isolation ring structure 112 andthe diffusion confining structure 114. For example, dimension d₇ is alsoreferred to herein as a first depth, and dimension d₂ is also referredto herein as a second depth, wherein the second depth d₂ is preferablysubstantially the same as the first depth d₇ in the embodiment shown inFIG. 2.

The isolation ring structure 112 and the diffusion confining structure114 are formed within a top portion of the workpiece 102 and preferablyextend completely through at least a portion of the buried layer 104, asshown. The isolation ring structure 112 and the diffusion confiningstructure 114 preferably also extend completely through the buried layer104 and partially into a portion of the workpiece 102 beneath the buriedlayer 104 by dimension d₆, as shown in FIG. 2.

After the liner 108 and fill material 110 are formed, a chemicalmechanical polish (CMP) process and/or an etch process may be used toremove the liner 108 and fill material 110 from over the top surface ofthe workpiece 102, leaving the structure shown in FIG. 2.

FIG. 3 shows the semiconductor device 100 of FIG. 2 after the workpiece102 is masked with a masking material 116 and a dopant element 118 isimplanted within the top portion of the workpiece 102 into a portion ofthe interior of the isolation ring structure 112. The dopant element 118preferably comprises at least one dopant element; e.g., the dopantelement 118 may comprise a plurality of dopant elements. The dopantelement 118 is preferably implanted into the top surface of theworkpiece 102 in a sinker contact region defined by an interior wall ofthe isolation ring structure 112 and one side of the diffusion confiningstructure 114, for example, as shown in FIG. 3, forming a sinker contact120.

The dopant element 118 preferably comprises an N type material in someembodiments, although alternatively, the dopant element 118 may alsocomprise a P type material, for example. The dopant element 118 maycomprise As, P, B, or other dopants or elements typically used inimplantation processes to make a semiconductive material such as theworkpiece 102 more conductive, for example.

FIG. 4 a shows a top view of the semiconductor device 100 shown in FIG.3 in accordance with an embodiment of the present invention. Theisolation ring structure 112 comprises a ring shape and has an interiorregion. Note that in this embodiment, the novel diffusion confiningstructure 114 preferably comprises an elongated isolation trench havinga length or dimension d₈. Dimension d₈ may comprise about 5 to 100 μm orless, for example, although alternatively, dimension d₈ may compriseother dimensions. The isolation trench of the diffusion confiningstructure 114 is preferably spaced apart at the ends of the isolationtrench from the isolation ring structure 112 by a dimension d₉, asshown. Dimension d₉ may comprise about 3 μm, for example, althoughalternatively, dimension d₉ may comprise other dimensions.

Preferably, the dopant element 118 is implanted into the workpiece 102by a dimension d₁₀ that is spaced apart from the ends of the diffusionconfining structure 114. Dimension d₁₀ may comprise about 3 μm orgreater, for example, although alternatively, dimension d₁₀ may compriseother dimensions. Dimension d₁₀ is preferably greater than dimension d₉in some embodiments, for example. The dimension d₁₀ is preferablyselected or designed such that after the diffusion of the dopant element118 and after drive-in of the dopant element 118 of the sinker contact120, the dopant element 118 does not reach the right side of thediffusion confining structure 114. The dopant element 118 preferablydoes not exceed the confined part of the sinker contact 120, e.g., theactive region of the workpiece 102 to the right of the diffusionconfining structure 114 in FIG. 4 a. In other words, the implantationarea of the sinker contact 120 is preferably smaller than the diffusionconfining structure 114 by a distance about equal to the diffusionlength during the subsequent sinker contact 120 dopant element 118drive-in, shown in FIG. 5 (to be described further herein).

In the embodiment shown in a top view in FIG. 4 a, the diffusionconfining structure 114 comprises an isolation trench that extends fromproximate a first side of the isolation ring structure 112 to proximatea second side of the isolation ring structure 112. The isolation trenchof the diffusion confining structure 114 comprises a first end and asecond end opposite the first end, wherein the first end and the secondend of the isolation trench are spaced apart from the isolation ringstructure 112 by a dimension d₉, allowing electrical connection of thesinker contact 120 to the buried layer 104 (see FIG. 5) proximate thefirst end and the second end of the isolation trench of the diffusionconfining structure 114.

In another embodiment, shown in FIG. 4 b, the diffusion confiningstructure 114 preferably is segmented, comprising an interrupteddiffusion confining structure 114, for example. The trenches for thediffusion confining structure 114 in this embodiment are preferablyformed by forming an isolation trench within the interior region of theisolating ring structure that comprises a plurality of trench segments.The trench structure of the diffusion confining structure 114 ispreferably interrupted with material comprised of the top portion ofworkpiece 102, the buried layer 104, and a portion of the lower portionof the workpiece 102, wherein the width of the workpiece 102 and buriedlayer 104 in the space between the trenches comprises a dimensionsimilar or equal to the spacings d₉ at the end of the trench segments,for example, as shown. Segmenting the trench of the diffusion confiningstructure 114 achieves a lower resistance for the connection of thesinker contact 120 to the buried layer 104 to the right of the diffusionconfining structure 114 in FIG. 4 b, for example.

In the embodiment shown in FIG. 4 b, the implanted sinker contact 120regions are preferably slightly smaller (e.g., by the diffusion lengthof the dopant element 118) than the trench segments of the diffusionconfining structure 114. The diffusion confining structure 114preferably comprises a plurality of regions of the diffusion confiningstructure 114, and the sinker contact 120 comprises a plurality ofsinker contact 120 regions. The plurality of sinker contact 120 regionseach provide electrical connection of the sinker contact 120 to theburied layer 104, providing an improved, lower ohmic electrical contactof the sinker contact 120 to the buried layer 104.

The workpiece 102 is then annealed to drive in the dopant element 118,as shown in FIG. 5, using an anneal process 122. The workpiece 102 maybe heated to a temperature of about 1,000 degrees C. or greater forabout an hour or more, although other temperatures and time durationsmay also be used for the anneal process 122. The anneal process or step122 causes diffusion of the dopant element 118 into the top surface ofthe workpiece 102, forming a sinker contact 120 that makes electricalcontact to and is coupled to the buried layer 104 within the workpiece102. A portion of the dopant element 118 may diffuse into a top portionof the buried layer 104, beneath the top surface 124 of the buried layer104, for example, as shown. The sinker contact 120 is also referred toherein as a conductive region, for example.

The diffusion confining structure 114 confines lateral diffusion of thedopant element 118 within the top portion of the workpiece 102 duringthe anneal process 122 on at least one side, e.g., on the side of theisolation trench of the diffusion confining structure 114 in theembodiment shown in a top view in FIG. 4 a, defining an edge of thesinker contact 120. The opposite edge of the sinker contact 120 isdefined by the interior wall of the isolation ring structure 112. Inother words, the diffusion confining structure 114 comprises anisolation trench, wherein the isolation trench defines a first edge ofthe conductive region 120, and the isolation ring structure 112 definesa second edge of the conductive region 120. The embodiment shown in FIG.4 b in a top view also defines a first edge of the conductive region 120in the shape of a plurality of segments.

FIG. 6 shows a top view of the embodiment shown in FIGS. 4 a and 5,illustrating that the sinker contact 120 makes electrical contact to theburied layer 104 at the ends of the isolation trenches of the diffusionconfining structure 114. Because the ends of the isolation trenches ofthe diffusion confining structure 114 are open, e.g., the workpiece 102remains intact between the ends of the diffusion confining structure 114and the isolation ring structure 112, diffusion of the dopant element118 reaches beyond the ends of the isolation trenches of the diffusionconfining structure 114, as shown at 126. Electrical contact of thesinker contact 120 104 confined by the diffusion confining structure 114to the buried layer 104 on the right side of 110 is made around the endsor edges of the diffusion confining structure 114. In the embodimentshown in FIG. 4 b, comprising the segmented diffusion confiningstructure 114, electrical contact of the sinker contact 120 to buriedlayer 104 is made at the ends and also through the spaces between thesegments of the diffusion confining structure 114, for example. The endsof the isolation trenches of the diffusion confining structure 114preferably do not extend fully to the isolation ring structure 112 inthe embodiments shown in FIGS. 4 a and 4 b, for example.

In the embodiment shown in FIGS. 1 through 4 a, 5, and 6, the noveldiffusion confining structure 114 confines diffusion of the sinkercontact 120 dopant element 118 in one dimension, e.g., defining theshape of the sinker contact 120 on one side. In the embodiment shown inFIG. 4 b, the diffusion confining structure 114 confines diffusion ofthe sinker contact 120 dopant element 118 in segments, also on one side.In other embodiments of the present invention, diffusion confiningstructures are used that further define the shape of the sinker contact120 in two dimensions.

FIGS. 7 and 8 show a cross-sectional view and a top view, respectively,of another preferred embodiment of the present invention, wherein adiffusion confining structure 214 comprises a second isolation ringstructure 214 formed within an interior of a first isolation ringstructure 212, and wherein a sinker contact 220 is formed in theinterior of the second isolation ring structure 214. Like numerals areused for the various elements that were described in FIGS. 1 through 6.To avoid repetition, each reference number shown in FIGS. 7 and 8 is notdescribed again in detail herein. Rather, similar materials x02, x04,x06, x08, etc . . . are preferably used for the various material layersshown as were described for FIGS. 1 through 6, where x=1 in FIGS. 1through 6 and x=2 in FIGS. 7 and 8. As an example, the preferred andalternative materials and dimensions described for the liner 108 andfill material 110 in the description for FIGS. 1 through 6 arepreferably also used for the liner 208 and fill material 210 shown inFIG. 7.

In this embodiment, the isolation ring structure 212 comprises a firstisolation ring structure, and the diffusion confining structure 214comprises a second isolation ring structure, the second isolation ringstructure 214 being disposed within the first isolation ring structure212. The conductive region 220 or sinker contact is formed in anddisposed within the second isolation ring structure 214. For example,the at least one dopant element is implanted within the top portion ofthe workpiece 202 into an interior of the second isolation ringstructure 214.

Note that in this embodiment, in order to make electrical contact withthe buried layer 204, the diffusion confining structure 214 preferablydoes not extend completely through the buried layer 204. Rather, thediffusion confining structure 214 preferably extends partially throughthe buried layer 204, as shown at dimension d₁₂ in FIG. 7. Dimension d₁₂may comprise about 2 μm or less, for example, although alternatively,dimension d₁₂ may comprise other dimensions.

The etch process to form the trenches for the isolation ring structure212 and diffusion confining structure 214 preferably comprises a RIEetch in this embodiment, for example, and the phenomena of RIE lag maybe used to form the trenches. In a RIE etch process, narrow openingsetch slower and result in shallower trenches than wide openings.Therefore, a single RIE etch process may advantageously be used to formboth deep and shallow trenches, by selecting trench openings or widthsthat will achieve the desired depth of the trenches.

For example, the diffusion confining structure 214 preferably comprisesa width comprising a dimension d₁₁ that is preferably less than thewidth d₄ of the isolation ring structure 212, as shown. Dimension d₁₁may comprise about 2 μm or less, for example, although alternatively,dimension d₁₁ may comprise other dimensions. Note that dimension d₁₁ isalso referred to herein as a second width (e.g., in the claims) anddimension d₄ is also referred to herein as a first width, the secondwidth being less than the first width, in this embodiment. The diffusionconfining structure 214 preferably has a narrower second width d₁₁ thanthe first width d₄ of the isolation ring structure.

A shallower depth d₁₃ of the diffusion confining structure 214 may beachieved using a RIE etch, which results in a shallower depth d₁₃ of thediffusion confining structure 214 than the depth of the isolation ringstructure 212 due to the narrower width d₁₁ of the diffusion confiningstructure 214. RIE lag of the RIE process causes the isolation ringstructure 212 to be formed deeper into the workpiece 202 than thediffusion confining structure 214. In other words, the isolation ringstructure 212 comprises a first depth (not labeled in FIG. 7; see FIG. 2at dimension d₇) within the workpiece 202, and the diffusion confiningstructure 214 comprises a second depth or dimension d₁₃ within theworkpiece 202, the second depth d₁₃ being less than the first depth d₇.Dimension d₁₃ may comprise about 11 μm or less, for example, althoughalternatively, dimension d₁₃ may comprise other dimensions. Due to RIElag, the narrower trenches of the diffusion confining structure 214 donot form as deeply as the wider trenches for the isolation ringstructure 212. Thus, the narrower trenches of the diffusion confiningstructure 214 form a narrow isolating ring that makes contact justwithin the buried layer 204, so that the diffusion confining structure214 advantageously completely encapsulates the sinker contact 220.

The diffusion confining structure 214 is used to define at least twoedges of the conductive region or sinker contact 220 in this embodiment.In the embodiment shown, for example, because contact is made on allfour sides of the sinker contact 220 by the diffusion confiningstructure 214, diffusion of dopant elements from the sinker contact 220is confined on all sides and is bounded on all edges of the sinkercontact 220 by the isolation ring structure 212.

The isolation ring structure 212 preferably extends completely throughthe buried layer 204 and partially into a portion of the workpiece 202beneath the buried layer 204 in this embodiment, and the diffusionconfining structure 214 preferably extends partially through the buriedlayer 204, as shown in FIG. 7.

FIG. 8 shows a top view of the semiconductor device 200 shown in FIG. 7.The ring shape of the diffusion confining structure 214 is visible inthe view of FIG. 8, for example. The diffusion confining structure 214may comprise a width in the top view or dimension d₁₄ of about 5 μm orgreater, for example, although alternatively, dimension d₁₄ may compriseother dimensions. The diffusion confining structure 214 may comprise alength or dimension d₁₅ of about 5 μm or less, for example, althoughalternatively, dimension d₁₅ may comprise other dimensions.

FIGS. 9 and 10 show a cross-sectional view and a top view, respectively,of another preferred embodiment of the present invention, wherein adiffusion confining structure 314 comprises an isolation trench thatextends partially through the buried layer 304 and completely from oneside to another of the isolation ring structure 312. Again, likenumerals are used to describe FIGS. 9 and 10 that were used to describethe previous drawings, and to avoid repetition, each element shown inFIGS. 9 and 10 is not described in detail herein again.

In this embodiment, the diffusion confining structure 314 comprises atrench that extends completely from a first side of the isolation ringstructure 312 to a second side of the isolation ring structure 312.However, to provide electrical contact between the buried layer 304 andthe sinker contact 320, the isolation trenches that comprise thediffusion confining structure 314 preferably extend only partially intothe buried layer 304 so that electrical contact may be made to otherregions of the buried layer 304 (e.g., to the right of the isolationtrenches 314 shown in FIGS. 9 and 10).

The diffusion confining structure 314 is used to define at least twoedges of the conductive region or sinker contact 320 in this embodiment.Because contact is made completely to either side of the isolation ringstructure 312, diffusion of dopant elements from the sinker contact 320is confined on three sides by the isolation ring structure 312, anddiffusion is confined on one side or edge by the diffusion confiningstructure 314. The length or dimension d₁₆ of the diffusion confiningstructure 314 may comprise about 5 to 100 μm, for example, althoughalternatively, dimension d₁₆ may comprise other dimensions.

In this embodiment, as in the embodiment shown in FIGS. 7 and 8, theisolation ring structure 312 comprises a dimension d₄ comprising a firstwidth, and the diffusion confining structure 314 comprises a dimensiond₁₁ also referred to herein as a second width, the second width d₁₁being less than the first width d₄. Because the diffusion confiningstructure 314 is narrower than the isolation ring structure 312, if theetch process to form the trenches for the isolation ring structure 312and the diffusion confining structure 314 comprise a RIE process, whichis preferable, RIE lag of the RIE process advantageously causes theisolation ring structure 312 to be formed deeper into the workpiece 302than the diffusion confining structure 314. Because the diffusionconfining structure 314 is narrower, the trenches are not formedcompletely through the buried layer 304 so that electrical contact ismade by the sinker contact 320 to the buried layer 304. Thus, theisolation ring structure 312 comprises a first depth (dimension d₇ shownin FIG. 2) within the workpiece 302, and the diffusion confiningstructure 314 comprises a dimension d₁₃, also referred to herein as asecond depth d₁₃, within the workpiece, the second depth d₁₃ being lessthan the first depth d₇.

As in the embodiment shown in FIGS. 7 and 8, the isolation ringstructure 312 preferably extends completely through the buried layer 304and partially into a portion of the workpiece 302 beneath the buriedlayer 304, to ensure adequate isolation from adjacent devices in theworkpiece 302, for example, not shown. The diffusion confining structure314 preferably extends only partially through the buried layer 304 toensure electrical contact with the buried layer 304, as shown atdimension d₁₂.

Embodiments of the present invention are beneficial when used to formsinker contacts 120, 220, and 320, e.g., in bipolar devices. Forexample, the sinker contacts 120, 220, and 320 may be used to makeelectrical contact to a buried layer 104, 204, or 304 that functions asa highly doped sub-collector used in a bipolar transistor. Anotherexample of an application in which embodiments of the present inventionmay be implemented is in smart power technologies, where a buried layer104, 204, or 304 may provide high voltage isolation from the substrate102, 202, or 302. In such applications, the buried layer 104, 204, or304 needs to be electrically connected by a sinker contact 120, 220, or320, for example. Another example of an application in which the novelsinker contacts 120, 220, and 320 of embodiments of the presentinvention may be implemented in, which is often found in smart powertechnologies, for example, is in vertical drain-extended MOStransistors, wherein an extended drain is formed vertically in theepitaxy on top of a buried layer 104, 204, or 304. In such applications,the sinker contact 120, 220, or 320 may function directly as a draincontact, for example. Alternatively, embodiments of the presentinvention may be implemented in other applications.

In the semiconductor devices 100, 200, and 300 shown in the drawings, aconductive line, a conductive pad, or a contact may be formed ordisposed over and adjacent to the conductive region or sinker contact120, 220, and 320, wherein the conductive region 120, 220, and 320provides electrical connection of the conductive line, conductive pad,or contact to an active area of the workpiece 102, 202, and 302, forexample.

Embodiments of the present invention achieve technical advantages byproviding novel structures for sinker contacts 120, 220, and 320 andnovel methods of manufacture thereof. The isolation ring structures 112,212, and 312 may be made smaller, with the use of the novel diffusionconfining structures 114, 214, and 314 within the isolation ringstructures 112, 212, and 312 in accordance with embodiments of thepresent invention. The width of the isolation ring structures 112, 212,and 312 may be reduced in semiconductor device designs, so that thesurface area may be used for active areas and other devices andcomponents, rather than for sinker contact areas, advantageously.Smaller isolation ring structures 112, 212, and 312 may be used, whereinthe isolation ring structures are smaller and require less space, yetstill effectively isolate the sinker contacts 120, 220, and 320 fromadjacent devices of the workpiece 102, 202, and 302. Furthermore,adjacent devices in the workpiece 102, 202, and 302 may be placed closerto the sinker contacts 120, 220, and 320 because the diffusion confiningstructures 114, 214, and 314 and the isolation ring structures 112, 212,and 312 provide trench isolation to adjacent devices. Thus,semiconductor devices 100, 200, and 300 may be scaled down further insize in accordance with embodiments of the present invention.

The widths and lateral sizes of sinker contacts 120, 220, and 320 mayalso be decreased, e.g., by controlling and limiting the width of thesinker contact 120, 220, and 320 diffusion using the novel diffusionconfining structures 114, 214, and 314 described herein. Implementingthe diffusion confining structures 114, 214, and 314 in a semiconductordevice 100, 200, and 300 allows for smaller sinker contacts 120, 220,and 320 to be formed. Sinker contacts 120, 220, and 320 comprising awidth of a few μm or less may be achieved in some applications inaccordance with embodiments of the present invention, for example

Advantageously, the diffusion confining structures 114, 214, and 314 arepreferably formed simultaneously with the formation of the isolationring structures 112, 212, and 312, so that additional lithography masks,lithography exposure steps, development steps, etch steps, and/ordeposition steps, are not required to form the novel diffusion confiningstructures 114, 214, and 314. Thus, the novel diffusion confiningstructures 114, 214, and 314 and sinker contacts 120, 220, and 320 areeasily and inexpensively implementable in manufacturing process flows,for example.

RIE lag of a RIE etch process used to form trenches for the isolationring structures 112, 212, and 312 and diffusion confining structures114, 214, and 314 may advantageously be utilized to achieve a desireddepth of the diffusion confining structures 114, 214, and 314, byselecting widths of the trenches for the diffusion confining structures114, 214, and 314 that will achieve the desired depth of the diffusionconfining structures 114, 214, and 314 during the particular RIE processused to form the isolation ring structures 112, 212, and 312, forexample.

Although embodiments of the present invention and their advantages havebeen described in detail, it should be understood that various changes,substitutions and alterations can be made herein without departing fromthe spirit and scope of the invention as defined by the appended claims.For example, it will be readily understood by those skilled in the artthat many of the features, functions, processes, and materials describedherein may be varied while remaining within the scope of the presentinvention. Moreover, the scope of the present application is notintended to be limited to the particular embodiments of the process,machine, manufacture, composition of matter, means, methods and stepsdescribed in the specification. As one of ordinary skill in the art willreadily appreciate from the disclosure of the present invention,processes, machines, manufacture, compositions of matter, means,methods, or steps, presently existing or later to be developed, thatperform substantially the same function or achieve substantially thesame result as the corresponding embodiments described herein may beutilized according to the present invention. Accordingly, the appendedclaims are intended to include within their scope such processes,machines, manufacture, compositions of matter, means, methods, or steps.

1. A semiconductor device, comprising: a workpiece including a buriedlayer disposed beneath a top portion of the workpiece; an isolation ringstructure disposed within the top portion of the workpiece extendingcompletely through at least a portion of the buried layer, the isolationring structure comprising a ring having an interior region; a diffusionconfining structure disposed within the interior region of the isolationring structure; and a conductive region disposed within the top portionof the workpiece within a portion of the interior of the isolation ringstructure, the conductive region comprising at least one dopant elementimplanted and diffused into the top portion of the workpiece, whereinthe diffusion confining structure defines at least one edge of theconductive region, and wherein the conductive region is coupled to theburied layer.
 2. The semiconductor device according to claim 1, whereinthe diffusion confining structure comprises a trench, wherein the trenchdefines a first edge of the conductive region, wherein the trenchincludes an insulating material disposed therein, and wherein theisolation ring structure defines a second edge of the conductive region.3. The semiconductor device according to claim 2, wherein the trenchextends from proximate a first side of the isolation ring structure toproximate a second side of the isolation ring structure, the trenchbeing spaced apart from the isolation ring structure.
 4. Thesemiconductor device according to claim 2, wherein the trench extendscompletely from a first side of the isolation ring structure to a secondside of the isolation ring structure.
 5. The semiconductor deviceaccording to claim 1, wherein the diffusion confining structure definesat least two edges of the conductive region.
 6. The semiconductor deviceaccording to claim 1, wherein the isolation ring structure comprises afirst isolation ring structure, wherein the diffusion confiningstructure comprises a second isolation ring structure, the secondisolation ring structure being disposed within the first isolation ringstructure, and wherein the conductive region is disposed within thesecond isolation ring structure.
 7. A semiconductor device, comprising:a workpiece including a buried layer disposed beneath a top portion ofthe workpiece, the buried layer being conductive and being coupled to anactive area of the workpiece; an isolation ring structure disposedwithin the top portion of the workpiece extending completely through atleast a portion of the buried layer, the isolation ring structurecomprising a ring having an interior region; a diffusion confiningstructure disposed within the interior region of the isolation ringstructure; and a conductive region disposed within the top portion ofthe workpiece within a portion of the interior of the isolation ringstructure, the conductive region comprising at least one dopant elementimplanted and diffused into the top portion of the workpiece, whereinthe diffusion confining structure defines at least one edge of theconductive region, wherein the isolation ring structure isolates theconductive region from adjacent devices disposed in the workpiece, andwherein the conductive region makes electrical contact to the buriedlayer.
 8. The semiconductor device according to claim 7, wherein theisolation ring structure comprises a first width, and wherein thediffusion confining structure comprises a second width, the second widthbeing substantially the same as the first width.
 9. The semiconductordevice according to claim 7, wherein the isolation ring structurecomprises a first width, and wherein the diffusion confining structurecomprises a second width, the second width being less than the firstwidth.
 10. The semiconductor device according to claim 7, wherein theisolation ring structure comprises a first depth within the workpiece,and wherein the diffusion confining structure comprises a second depthwithin the workpiece, the second depth being substantially the same asthe first depth.
 11. The semiconductor device according to claim 7,wherein the isolation ring structure comprises a first depth within theworkpiece, and wherein the diffusion confining structure comprises asecond depth within the workpiece, the second depth being less than thefirst depth.
 12. The semiconductor device according to claim 7, furthercomprising a conductive line, a conductive pad, or a contact disposedover and adjacent to the conductive region, and wherein the conductiveregion provides electrical connection of the conductive line, conductivepad, or contact to the active area of the workpiece.
 13. Thesemiconductor device according to claim 12, wherein the active areacomprises a portion of a transistor, diode, capacitor, logic device,memory device, other circuit elements, or combinations thereof.
 14. Amethod of manufacturing a semiconductor device, the method comprising:providing a workpiece having a buried layer disposed therein; forming anisolation ring structure within a top portion of the workpiece, theisolation ring structure extending completely through at least a portionof the buried layer, the isolation ring structure comprising a ringhaving an interior region; forming a diffusion confining structurewithin the interior region of the isolation ring structure; implantingat least one dopant element within the top portion of the workpiece intoa portion of the interior of the isolation ring structure; and heatingthe workpiece, causing the at least one dopant element to diffuse withinthe top portion of the workpiece and form a conductive region, theconductive region being coupled to the buried layer, wherein thediffusion confining structure confines lateral diffusion of the at leastone dopant element within the top portion of the workpiece on at leastone side.
 15. The method according to claim 14, wherein forming thediffusion confining structure comprises forming a trench within theisolation ring structure, and disposing an insulating material withinthe trench; and wherein implanting the at least one dopant elementwithin the top portion of the workpiece comprises implanting the atleast one dopant element between the trench and a side of the isolationring structure.
 16. The method according to claim 15, wherein formingthe diffusion confining structure comprises forming an insulating linerwithin the trench, and forming a semiconductive material over theinsulating liner within the trench.
 17. The method according to claim14, wherein forming the isolation ring structure comprises forming afirst isolation ring structure, wherein forming the diffusion confiningstructure comprises forming a second isolation ring structure, thesecond isolation ring structure being disposed within the firstisolation ring structure, wherein implanting the at least one dopantelement within the top portion of the workpiece into the portion of theinterior of the first isolation ring structure comprises implanting theat least one dopant element into an interior of the second isolationring structure.
 18. The method according to claim 14, wherein formingthe isolation ring structure and forming the diffusion confiningstructure comprise forming a masking material over the workpiece,patterning the masking material with a pattern for the isolation ringstructure and the diffusion confining structure, etching away portionsof the workpiece using the masking material as a mask, and removing themasking material.
 19. The method according to claim 14, wherein formingthe isolation ring structure and forming the diffusion confiningstructure comprise forming the isolation ring structure and thediffusion confining structure simultaneously using a single etchprocess.
 20. A method of forming a sinker contact for a semiconductordevice, the method comprising: providing a workpiece having a buriedlayer disposed therein, the buried layer being conductive and beingcoupled to an active area of the workpiece; forming an isolation ringstructure within a top portion of the workpiece, the isolation ringstructure extending completely through at least a portion of the buriedlayer, the isolation ring structure comprising a ring having an interiorregion; forming a diffusion confining structure within the interiorregion of the isolation ring structure; implanting at least one dopantelement within the top portion of the workpiece into a portion of theinterior of the isolation ring structure; and heating the workpiece,causing the at least one dopant element to diffuse within the topportion of the workpiece and form the sinker contact, the sinker contactbeing coupled to the buried layer, wherein the diffusion confiningstructure confines lateral diffusion of the at least one dopant elementwithin the top portion of the workpiece on at least one side, definingat least one edge of the sinker contact, and wherein the isolation ringstructure isolates the sinker contact from an adjacent device of theworkpiece.
 21. The method according to claim 20, wherein the diffusionconfining structure is narrower than the isolation ring structure,wherein the single etch process comprises a reactive ion etch (RIE)process, and wherein RIE lag of the RIE process causes the isolationring structure to be formed deeper into the workpiece than the diffusionconfining structure.
 22. The method according to claim 21, whereinforming the isolation ring structure comprises forming an isolation ringstructure that extends completely through the buried layer and partiallyinto a portion of the workpiece beneath the buried layer, and whereinforming the diffusion confining structure comprises forming a diffusionconfining structure that extends partially through the buried layer. 23.The method according to claim 20, wherein forming the diffusionconfining structure comprises forming an isolation trench that extendsfrom proximate a first side of the isolation ring structure to proximatea second side of the isolation ring structure, the isolation trenchcomprising a first end and a second end opposite the first end, whereinthe first end and the second end of the isolation trench are spacedapart from the isolation ring structure, allowing electrical connectionof the sinker contact to the buried layer proximate the first end andthe second end of the isolation trench.
 24. The method according toclaim 23, wherein forming the isolation trench comprises forming anisolation trench that comprises a plurality of trench segments.
 25. Themethod according to claim 23, wherein forming the isolation ringstructure comprises forming an isolation ring structure having a firstwidth and a first depth, and wherein forming the diffusion confiningstructure comprises forming an isolation ring structure having a secondwidth and a second depth, wherein the first depth is substantially thesame as the second depth, and wherein the first width is substantiallythe same as the second depth, and wherein the first depth and the seconddepth extend completely through the buried layer and partially into aportion of the workpiece beneath the buried layer.
 26. The methodaccording to claim 20, wherein forming the diffusion confining structurecomprises forming an isolation trench that extends completely from afirst side of the isolation ring structure to a second side of theisolation ring structure, wherein forming the isolation ring structurecomprises forming an isolation ring structure that extends completelythrough the buried layer and partially into a portion of the workpiecebeneath the buried layer, and wherein forming the isolation trench ofthe diffusion confining structure comprises forming an isolation trenchthat extends partially through the buried layer.
 27. The methodaccording to claim 20, wherein forming the isolation ring structurecomprises forming a first isolation ring structure, wherein forming thediffusion confining structure comprises forming a second isolation ringstructure, the second isolation ring structure being disposed within thefirst isolation ring structure, wherein implanting the at least onedopant element comprises implanting the at least one dopant within thesecond isolation ring structure, wherein forming the first isolationring structure comprises forming an isolation ring structure thatextends completely through the buried layer and partially into a portionof the workpiece beneath the buried layer, and wherein forming thesecond isolation ring structure comprises forming a second isolationring structure that extends partially through the buried layer.